The invention relates to a machine tool, wherein the machine tool has a workpiece clamping device for clamping a workpiece. The invention relates furthermore to a corresponding method.
On machine tools, machining forces occur between the tool and the workpiece, in particular during milling or turning. Depending on the dynamic compliance of the machine tools on the one hand, but also governed by technological parameters of the cutting process and the material of the workpiece on the other hand, there develops on the tool an interaction that establishes the relationship between the machining forces and the resultant deflections of the tool. Such an interaction can be made unstable, if for example the cutting width is chosen to be too great for the required cutting frequency, i.e. if the infeed is too fast. As a result, machine elements, the tool and/or the workpiece, undergo vibrations, in particular what are known as chatter vibrations. These clearly audible chatter vibrations leave what are known as chatter marks on the surface of the workpiece, which are generally unacceptable for the quality of the surface. For this reason, measures must be taken to avoid the vibrations.
A common procedure is to make the cutting process more conservative, by reducing the cutting width that is actually desired. However, this measure means increasing the machining time, and consequently reducing the efficiency of the machine.
Another approach is to determine the dynamic compliance of the machine tool and use a modal analysis to assign critical resonances occurring therein to the individual regions of the machine. By such an analysis, it can be established which regions of the machine have excessive compliance in comparison with the cutting process and are causally responsible for the chatter vibrations, i.e. the chattering. It is, however, difficult to remedy the situation in accordance with the findings obtained. Usually, the machine compliance cannot be reduced in the corresponding frequency ranges by a specific measure (for example increasing the stiffness of discrete components of the machine), but rather it is often necessary for the machine to be comprehensively reconstructed or even changed in its fundamental design. In the case of an already existing machine, this approach is in any case unfeasible.
German Offenlegungsschrift DT 25 20 946 A1 discloses a method for preventing or eliminating chatter vibrations of a working spindle of machine tools and a device for carrying out this method.
DE 698 04 982 T2 discloses a device and method for recommending dynamically preferred machining speeds.
Offenlegungsschrift DE 44 05 660 A1 discloses a method and an arrangement for operating a metal-removing machine tool, in particular a circular sawing, milling or grinding machine or the like.
Offenlegungsschrift DE 102 29 134 A1 discloses a device and a method for machining workpieces with rotating tools, in which, to reduce vibrations, a rotating tool is dynamically moved with respect to the driveshaft by an adjusting unit provided in a rotating system between the driveshaft and the tool.
Offenlegungsschrift DE 198 25 373 A1 discloses clamping a tool in a tool holding fixture, wherein vibrations occurring are reduced with the aid of a compliant, highly damping element which is inserted in the flux of force between the tool and the tool holding fixture.
Offenlegungsschrift DE 102 20 937 A1 discloses a method and a device